The Internal Flow Field Modeling, Simulation And Experiment In The Oil-free Scroll Compressor Chamber

Scroll compressors are small size, light weight, less wearing parts and without reciprocating mechanism and own. They have great performance advantages in small and medium capacity compressors. They are main development direction of high performance compressors. The structure of oil-free scroll compressor precludes the possibility that working medium contacts with lubricants, which meet the specific needs of medical, food and other industry. However, the manufacturer of large displacement, long life oil-free scroll compressor is still difficult. In order to deeply understand the operation of the scroll compressor, and guide the design of the scroll compressor based on the principle, the analysis of the flow process in scroll compressor is very important. The thermodynamic and computational fluid dynamics theory are applied to study the scroll compressor’s internal flow process in this paper, and the transient distribution of pressure, temperature, flow velocity is gain for the design reference of high performance compressors.Firstly, the oil-free scroll compressor’s structure and working principle are introduced. According to the compression chamber geometry, based on the theory of thermodynamics and heat transfer, by Laws of mass and energy conservation, the volume change and thermodynamic process in the compression chamber are analyzed in detail. In this paper, the oil-free scroll compressor thermodynamic simulation models taking full account of the heat exchanger and the compression process leaks are proposed. The accuracy of mathematical models has been verified by the actul measured value.Then the flow field mathematical model and numerical simulation method are analyzed. The discharge process of scroll compressor is deemed as quasi-static process and the scoll compressor is analyzed by steady-state method of computational fluid dynamics. The reasonable geometric model of exhaust model is selected. The mesh independence is verigied in tests and last the exhaust process is simulated based turbulence theory. This simulation shows the velocity field in scroll compressor at different axial cross section and different vortex angular as well as the three-dimensional velocity field including exhaust pipe.And then the geometric model of scroll compressor is simplified. The compression chamber internal flow simulation is realized by using two-dimensional geometric model. Althought the geomety of scroll compressor is very complex, a suitable mesh form for scroll compressor flow field simulation is found. During the simulation, local deformation coupled with remeshing in CFD dynamicmesh technique is applied, under the condition of a compressible ideal gas, and the flow governing equations as well as the equation of gas state is followed. The RNG κ-ε model is used for turbulent model. This simulation detailedly displays the distribution of the compression chamber pressure, temperature, velocity distribution in the course of suction, compression, and exhaust in two-dimensional scroll compressor. The temperature, pressure, velocity variation at different speed is compared. The experimental results verify the correctness and validity of simulation.Finally,three-dimensional simplified geometric model of scroll compressor is designed. The triple prism mesh that is suitable for3-D scroll compressor flow field simulation is identified by comparing other meshes. The3-D transient simulation is achieved by using dynamic mesh and interface technology. The simulation vividly reveals3-D flow law within the scroll compressor and the temperature, pressure, flow velocity at each angular are given. The3-D results are compared with both2-D results and actual values, meanwhile, the reasons for the error difference are analyzed.The internal flow field simulation vividly reveals the flow law in scroll compressor. It’s important theoretical reference for in-depth study of the oil-free scroll compressor mechanism and solving the oil-free scroll compressor problems of short life and low displacement. Meanwhile, a new application area of CFD technique is explored due to the application of dynamic mesh technology for internal flow flield. It widens the application area of dynamic mesh technology.